There are known in the art vehicle theft prevention systems in which the position of a vehicle is measured by using a GPS (Global Positioning System) receiver which is fixedly mounted in a vehicle and receives signals from GPS satellites via a GPS antenna. When the vehicle is stolen, a transmitter in the vehicle transmits the position of the vehicle, and a central station pursues the position of the concerned vehicle.
However, many thieves have found ways to overcome theft prevention systems in which GPS information is utilized by breaking the GPS antenna. In such a case, no signal arrives at the vehicle and the theft prevention systems cannot be utilized.
Other vehicle theft prevention systems which are known in the art include immobilizer circuits which disable the vehicle's engine upon detection of a theft or an unauthorized movement of the vehicle.
Some of the theft prevention systems which are found in the art are described hereinbelow.
Japanese Patent Application JP 08136639 describes a method which involves measuring the position of a concerned vehicle (V) by a GPS receiver which is mounted on each vehicle. For each vehicle a predetermined management area (A) is set beforehand. The set management area is compared with the management area detected by the GPS receiver during theft. A radio mounted on the vehicle indicates the position of the theft vehicle. A vehicle administration bureau (M) pursues the position of the concerned vehicle. The position of the other external vehicle in the predetermined management area is also pursued.
Belgian Patent Application BE 1007815 describes a system which is linked via internal antennas, a built in communications module and communications satellites to one or more automatically operated earth based centers. The system has sensors which detect horizontal or vertical movements of the vehicle, unauthorized use or attempts to disable the system. The system has an "intelligent interpretation unit" which controls the communications signal exchanges and drives a visual signal unit. If the system or the remote center determines that the vehicle is being moved without authorization, the engine can be disabled.
World Patent Application WO 9513943 describes a system for remotely tripping a switch which uses a receiver which is located in the remote location. An unassisted telephone call is made by the owner, who is located in the remote location, and intercepted by the receiver. A tripping circuit responds to the receiver and trips a switch. Preferably, upon receiving the signal, the receiver sends an input signal to the tripping circuit. In response to the signal the tripping circuit trips the switch, thereby interrupting the vehicles ignition, and/or activates a vehicle alarm system or vehicle homing transmitter. The unassisted telephone call includes a predetermined remote location telephone number and a predetermined security code. The telephone number corresponds to the remote receiver.
French Patent Application FR 2709853 describes a system in which satellites generate signals which are received by a car installation. The car has a satellite antenna and receiver allowing the signals to locate the car position, and create digital navigation information. If the car alarm has been set off, this navigation information is passed to a central radio-communication tower. The tower passes the information to a central unit where the positional information is processed. The information is passed to a message acquisition module and placed in memory. The positional information is then verified by a calculator and finally passed to a man/machine interface to be displayed.
German Patent Application DE 4321417 describes an alarm device installed in or on the missing vehicle, or a pulse triggered by an external interrogating radio signal, which initiates the transmission of encoded radio signals by an on-board transponder. A wide-area network of reception sites for the transponder outputs is connected to a central station where the received signals are processed together with the map references of vehicles and/or the sites at which their transmissions are detected.
U.S. Pat. No. 5,223,844 describes a mobile unit which includes an input unit, responsive to an event or condition associated with a vehicle, and which provides information describing the event or condition. A satellite receiver, responsive to navigation signals transmitted by a satellite navigation system, provides information inherently describing the vehicle's location based on the navigation signals. A mobile unit controller, responsive to the input unit and the satellite receiver includes a cellular telephone transmitter for transmitting information onto a cellular telephone communication link.
World Patent Application WO 9305490 describes an alarm system in which a locator determines a vehicle position via global positioning signals from a satellite, at predetermined time intervals. A memory stores at least the most recent coordinate in memory and a transmitter sends signals to a remote facility when a trigger unit is actuated.
German Patent Application DE 4203865 describes apparatus which includes a location device which determines the actual position of a vehicle via satellite location in specific time intervals. A radio transmitter sends signals when a trigger device is actuated contingent the momentary or last specific position of the vehicle. A memory unit stores at least the last specific position of the vehicle and the radio transmitter may be tuned to the receiving equipment of emergency services. The release device has an alarm wire which activates the signal when a break-in occurs, and which is arranged in the closure or hinge area of a container or space to be secured and/or for securing a container walling.
U.S. Pat. No. 4,918,425 describes a transponder which responds to signals transmitted by a base station and indicates by an alarm the absence of appropriate response from the transponder. The base is capable of participating in homing techniques to locate a load transponder. A list of the IDs of all transponders reported missing is distributed from a central source by nationwide communication to a network of radio stations. Each station broadcasts the list in an encoded signal in repetitive sequence along with regular programming.
German Patent Application DE 3805810 describes a road vehicle which has an on board computer that operates together with the vehicle radio to provide a signal transmission link that enables the location of the vehicle to be fixed. The vehicle is identified by a code that is stored in system memory. The vehicle movement is related to road maps and is fixed by a navigation system which can be provided by satellite. Information regarding vehicle speed and location can be transmitted over the radio communication system. In the event of theft the location can be fixed. Any damage to the aerial causes an alarm to triggers.
French Patent Application FR 2541801 describes a surveillance system which includes a permanent emergency station equipped with a radio. A set of mobile alarm units are attached to each of the vehicles to be protected. Each alarm unit includes a system using signals emitted by satellites to locate its position, a compass, and a speed detector to sense its movement. The last two components allow movement of the vehicle to be monitored between the passage of satellites. The alarm units also include an interface and keyboard for control codes, as well as batteries and detectors sensing attempted theft.